1. Field of the Invention
This invention relates to a control unit having a function of inferring causes for various problems relating to a machine as an object of control, such as problems in the machine as an object of control, problems in a product processed by the machine as an object of control and the like, and countermeasures for dissolving the causes, and more particularly, to a control unit using a so-called expert system in which the knowledge and experiences of high-level specialists in the relating field are accumulated.
2. Description of the Related Art
As a system which infers causes for problems relating to a machine as an object of control and the most suitable countermeasure plans for dissolving the causes, there is a system using a so-called expert system. In the expert system, know-how, that is, knowledge possessed by specialists relating to a specific technique is stored as a knowledge base. When there arises a situation in which the judgment of specialists is required, inference for countermeasure plans is performed by a computer according to the knowledge base so that a correct judgment can be provided as if there exist specialists even when they are absent. The application of this system to various industrial fields is now attracting notice. As a paper describing the application of the expert system to an injection machine the setting of operation conditions of which is considered to be very difficult, there is "Expert Systems for Injection Molding" by Paul M. Menig et al. presented at the meeting "Artificial Intelligence for the Automotive Industry" held on Mar. 11-13, 1986. According to the system presented in this paper, countermeasures for problems are inferred in accordance with the inputs of data on the situations of the problems, various conditions and the like. However, since the system shown in this paper uses a fixed table, that is, a trouble shooting guide provided by DuPont Corp. for determining countermeasure plans for problems in molding, the system has the disadvantages that it is impossible to determine countermeasure plans which must essentially be judged according to the situations of the problems, and time is required or it is sometimes impossible to solve the problems, when there exist, for example, countermeasures which conflict with one another. Furthermore, the system of this paper only asks whether or not the problem has been solved after the execution of a certain countermeasure plan, and actions taken when other problems have occurred as a result of the measures or the situation has changed as a result of the countermeasure are not clear. Hence, it is difficult to operate the system as an expert system from a practical point of view.
As a known example in which the expert system has been applied to other fields, there is a system disclosed in Japanese Patent Public Disclosure (Kokai) No. 62-6845 (1987). In this disclosure, the expert system has been applied to a trouble diagnosis apparatus for vehicles.
However, although the system of this disclosure can be applied to the trouble diagnosis of vehicles, it is unsuitable for complicated control, such as control for an injection machine, that is, the control of the setting of operation conditions of the injection machine, and the like. That is, in the case of an injection machine, the production of good products, for example, sometimes becomes impossible not because the machine and the system do not have troubles, but because the setting of conditions is wrong. The setting of conditions is therefore difficult. For the setting of conditions, an action by combination of various kinds of conditions is required. Hence, the knowledge and experiences of high-level specialists which are totally different from those in the case of the trouble diagnosis of vehicles become necessary.
As described above, since the conventional apparatuses determine a countermeasure plan using a fixed table, they cannot provide actions, for example, when there exist countermeasure plans which conflict with one another, or they cannot be applied to the control of injection molding and the like.
It is an object of the present invention to provide a control apparatus having a inference function in which it is possible to infer countermeasures for problems occurred in a machine as an object of control with least human intervention and to execute the countermeasures inferred.
It is another object of the present invention to provide a control apparatus having an inference function which can control the setting of operation conditions of an injection machine and the like without having specialized knowledge and experiences, and which can deal with various situations.